Blair, a retired Navy admiral, is the third director of national intelligence, a position created in response to public outrage over the failure to prevent the Sept. 11, 2001, terrorist attacks.

His departure underscores the disorganization inside the Obama administration's intelligence apparatus, rocked over the past six months by a spate of high-profile attempted terror attacks that revealed new national security lapses. And it comes two days after a stark Senate report criticized Blair's office and other intelligence agencies for new failings that, despite a top-to-bottom overhaul of the U.S. intelligence apparatus after 9/11, allowed a would-be bomber to board a Detroit-bound airliner on Christmas Day.

In a message Thursday to his work force, Blair said his last day would be May 28.

"It is with deep regret that I informed the president today that I will step down as director of national intelligence," Blair said.

The resignation became inevitable following a meeting between President Barack Obama and Blair on Thursday afternoon, according to two senior congressional officials. During the meeting, the officials said, it became clear that Blair had "lost the confidence of the president."

Obama made no reference to Blair's rocky tenure in a brief statement Thursday night that did not acknowledge his impending resignation, one of the highest-profile administration departures.

"During his time as DNI, our intelligence community has performed admirably and effectively at a time of great challenges to our security, and I have valued his sense of purpose and patriotism," the president said. "He and I both share a deep admiration for the men and women of our intelligence community, who are performing extraordinary and indispensable service to our nation."

Two other government officials said several candidates already had been interviewed for the national intelligence director's job, which is to oversee the nation's 16 intelligence agencies.

"We have been interviewing several strong candidates to be his replacement," one official said.

All the officials spoke on condition of anonymity because the announcement had not yet been made. Blair's departure was first reported by ABC News.

Names mentioned as possible replacements for Blair include John Brennan, the president's homeland security and counterterrorism adviser; James R. Clapper, the undersecretary of defense for intelligence, and John Hamre, the president of the Center for Strategic and International Studies.

In an e-mail Thursday night, Hamre said: "I have had no conversations with anyone about the job and wish to remain at CSIS."

Blair's term in office was marred by turf battles with CIA Director Leon Panetta and Blair's own controversial public comments in the wake of the abortive Christmas Day jetliner bombing.

The two congressional officials said Blair had been on a losing streak since he squared off with Panetta last May over Blair's effort to choose a personal representative at U.S. embassies to be his eyes and ears abroad, instead of relying on CIA station chiefs, as had been past practice.